The present invention claims priority from Japanese Patent Application No. 9-163175 filed Jun. 20, 1997, which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a magnetic recording device and, particularly, to a detection of a write abnormality of the same magnetic recording device.
2. Description of Related Art
In order to detect an open-circuit or short-circuit abnormality of a write magnetic head of a conventional magnetic recording device, a head drive circuit thereof includes a head abnormality detection circuit. In a general head abnormality detection circuit, the normality of a head current is monitored by detecting a level of a counter electromotive force pulse voltage generated at switching time of the head current. That is, when an abnormality such as open-circuit or short-circuit is generated in the magnetic head, voltage having a predetermined level is not detected, from which the abnormality of the magnetic head can be detected. When such abnormality is detected, the head abnormality detection circuit outputs a fault pulse with which the head drive circuit enters into a write interruption mode.
FIG. 1 shows a construction of a magnetic recording device disclosed in Japanese Patent Application Laid-open No. Sho 64-13204, as an example of the prior art device. In this example, collectors of transistors 101 and 102 are connected to opposite terminals of a write magnetic head 51 and to set terminals of flip-flops 106 and 107, respectively, and collectors of transistors 103 and 104 are connected to opposite terminals of a magnetic head 52 and to reset terminals of the flip-flops 106 and 107, respectively. Write data a and b are connected to bases of the respective transistors 101 and 102. When the write data a becomes high level, the transistor 101 is turned on and a current flows through the head 51 is a direction 53. On the other hand, when the write data b becomes high level, the transistor 102 is turned on and a current flows through the head 51 in a direction opposite to the direction 53. In a case where a current flows through the head 51 normally, the opposite terminals of the head 51 become low level for either the write data a or b and the flip-flops 106 and 107 are set.
Similarly, when a current flows through the head 52 normally, the flip-flops 106 and 107 are set. On the other hand, an abnormality detection circuit 108 is input with outputs e and f of the flip-flops 106 and 107 and a logical sum t of write signals a, b, c and d and it is judged, from these three signals, whether or not the magnetic heads 51 and 52 are open-circuited.
In the prior art example, however, there is a problem that the head abnormality detection circuit malfunctions. That is, the condition for such as over-write or non-linear bit shift becomes more severe with increase of the data transfer rate and the probability of malfunction is increased due to noise overlapped on a power source and/or a grounding line or influence of inductance thereof, so that the head abnormality detection circuit malfunctions even when a normal write current flows through the heads. When such erroneous operation of the head abnormality detection circuit occurs, the magnetic recording device which is operating normally is decided as having an open-circuit or short-circuit abnormality and the write operation of the device is interrupted.